The background of the present invention is the field of orienting/positioning devices, which shall now be explained with reference to FIGS. 1 and 2. FIG. 1 shows a stereo camera, which can be directed in several degrees-of-freedom. It is now assumed that the shown camera is to be directed such that a detected visual target present somewhere in the input space of the camera moves into the origin of the input space. FIG. 2 shows a known process to calculate and carry out an action such as movement of the camera in order to achieve said object. In a first step the output of the sensor, here a camera, is evaluated to make a decision regarding a target position in the multi-dimensional input space of the sensor, which target position can e.g. be a recognized sound source. In a further step the sensor coordinates, such as angles etc. . . . are mapped into the motor coordinates such as voltages, currents etc. . . . using a predefined look-up table or analytical function in order to generate the actuator (motor) command necessary for the before decided new orientation of the camera.
Typical examples for sensors providing explicit orientation information are an image sensor array, a radar image sensor array or a chemical receptor sensor array. A typical sensor providing implicit orientation information is the use of stereo microphones to localize a sound source. For sensors providing implicit orientation information, the orientation information is typically extracted before said orientation information can be used.
Robots comprising sensors that supply orientation information are known as orienting robots. It is a disadvantage of such orienting robots that they frequently require calibration to work properly. Such calibration must be done after every change in system geometry, for example when the physical relation between a sensor and an actuator of the robot is changed, after every modification, for example lens replacement or motor modification, and if the robot is used in a changing or uncontrolled environment.
In certain environments a manual calibration by a user is not possible or desired, for example if the robot is a probe sent to a foreign planet. Furthermore, in case of frequent changes in system geometry, frequent modification of the sensors or motors or an uncontrolled environment, frequent calibration is very time consuming and laborious.
Therefore, there is a need for self-calibrating orienting robots. Conventional self-calibrating orienting robots use techniques such as calibration scenarios, mathematical analysis or parameter/hardware tuning with human supervision. All of the above calibration techniques suffer from one of the following disadvantages.
The use of calibration scenarios normally requires the return of actuators of the robot to reference points. Therefore, calibration in a new and/or uncontrolled environment frequently is not possible. Moreover, said calibration by using reference points frequently is not sufficient to solve the problem of non-linearity of motor responses.
Calibration by mathematical analysis has the drawback that several implicit assumptions are necessary which frequently result in strong simplifications. Often only a subset of variations is taken into account. Thus, the accuracy of said calibration method usually is insufficient. Furthermore, calibration by mathematical analysis frequently is not applicable for online calibration due to the high complexity. Finally, the analysis has to be re-defined for any voluntary or involuntary change of the set-up.
Parameter/hardware tuning with human supervision has the drawback that it requires human expert intervention. Therefore, this calibration solution is not suitable for autonomous robots. Moreover, this calibration technique usually is very time consuming and highly depends on the experience of the expert.
Therefore, there is a need for a method of controlling an orienting system and a self-calibrating orienting system, which allows an auto-calibration of the system without human intervention with high accuracy.
Further, there is a need for a method of controlling an orienting system and a self-calibrating orienting system which is adapted to deal with non-linearities in motor/sensor responses and which is adapted to be used in a changing and/or uncontrolled environment where maintenance is not possible or desired.